In general, a refrigerant circuit of an air-conditioning apparatus includes a compressor, a condenser, an expansion valve, and an evaporator. The air-conditioning apparatus is configured to suck, compress, and discharge refrigerant repeatedly by the compressor. Through repeated operation of the air-conditioning apparatus, the refrigerant is discharged in a pulsed manner, with the result that pressure of the refrigerant fluctuates. This phenomenon is called a pressure pulsation. There is a problem in that the pressure pulsation may be transmitted from the compressor through a discharge pipe of the compressor to an indoor-side heat exchanger, and cause resonance with the structure of the indoor-side heat exchanger, resulting in generation of noise. This noise is referred to as a pulsation noise.
Thus, in the refrigerant circuit of the air-conditioning apparatus, a muffler is mounted to a pipe extending from a discharge port of the compressor to the indoor-side heat exchanger to reduce the pulsation noise.
When basic characteristics of the muffler are taken into account, in order to enhance a muffling effect, a cross sectional area ratio of an expansion chamber of a muffler main body to a pipe connected to a muffler main body needs to be set large. In view of such circumstance, for example, there has been proposed a muffler employing a configuration in which an inner diameter of the muffler main body is set large so that the muffling effect is enhanced when the cross sectional area of the pipe is fixed (see, for example, Patent Literature 1).
Further, in order to achieve downsizing of the muffler, there has been proposed a muffler downsized by changing a length and a diameter of an insertion pipe inserted into the muffler main body (see, for example, Patent Literature 2). In the muffler according to Patent Literature 2, a muffling property is enhanced by reducing an inner diameter of an inlet pipe connected to an inlet of the muffler main body before the inlet pipe enters the muffler main body, and by positioning a distal end of a portion of the inlet pipe, which is inserted into the muffler main body, at a center of the muffler main body.